Process for production of hexamethylenediamine from carbohydrate-containing materials and intermediates therefor

ABSTRACT

Processes are disclosed for the conversion of a carbohydrate source to hexamethylenediamine (HMDA) and to intermediates useful for the production of hexamethylenediamine and other industrial chemicals. HMDA is produced by direct reduction of a furfural substrate to 1,6-hexanediol in the presence of hydrogen and a heterogeneous reduction catalyst comprising Pt or by indirect reduction of a furfural substrate to 1,6-hexanediol wherein 1,2,6-hexanetriol is produced by reduction of the furfural substrate in the presence of hydrogen and a catalyst comprising Pt and 1,2,6-hexanediol is then converted by hydrogenation in the presence of a catalyst comprising Pt to 1,6 hexanediol, each process then proceding to the production of HMDA by known routes, such as amination of the 1,6 hexanediol. Catalysts useful for the direct and indirect production of 1,6-hexanediol are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/290,869, filed on May 29, 2014, which is a continuation of U.S.application Ser. No. 13/739,975, filed Jan. 11, 2013, now issued as U.S.Pat. No. 8,853,458, which claims the benefit under 35 U.S.C. 119(e) ofU.S. Provisional Application No. 61/588,093, filed on Jan. 18, 2012, thedisclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND I. Field

The present disclosure relates generally to processes for conversion ofa carbohydrate source to hexamethylenediamine and to intermediatesuseful for the production of hexamethylenediamine and other industrialchemicals. The present disclosure relates more specifically tochemocatalytic processes for the production of hexamtheylenediamine froma furfural substrate derived from a carbohydrate source, which substrateis converted to an intermediate comprising 1,6-hexanediol from which thehexamethylenediamine can be derived by chemocatalytic amination of thediol. The present invention is also directed to the production of1,6-hexanediol from a furfural substrate in which at least a portion ofthe furfural substrate is converted to 1,2,6 hexanetriol, at least aportion of the hexanetriol is then converted to 1,6-hexanediol, and the1,6 hexanediol is then converted to hexamethylenediamine by, forexample, chemocatalytic amination of the diol. The present disclosurealso relates to improved processes for the production of hexanediol froma furfural substrate.

II. Background

Hexamethylenediamine (HMDA) is a chemical intermediate primarily used inthe production of nylon 6,6 via a condensation with adipic acid. HMDA isalso used in the production of monomers for polyurethanes. Further, HMDAis used in the production of epoxy resins. Today, annual production ofHMDA exceeds 3 billion pounds (avoir).

Crude oil is currently the source of most commodity and specialtyorganic chemicals. Many of these chemicals are employed in themanufacture of polymers and other materials. Desired chemicals include,for example, styrene, bisphenol A, terephthalic acid, adipic acid,caprolactam, hexamethylenediamine, adiponitrile, caprolactone, acrylicacid, acrylonitrile, 1,6-hexanediol, 1,3-propanediol, and others. Crudeoil is first refined, typically by steam cracking, into hydrocarbonintermediates such as ethylene, propylene, butadiene, benzene, andcyclohexane. These hydrocarbon intermediates then typically undergo oneor more catalytic reactions by various processes to produce thesedesired chemical(s).

HMDA is among those chemicals that continue to be produced commerciallyfrom oil via a multistep process. HMDA is typically produced frombutadiene. Butadiene is typically produced from steam cracking ofheavier feeds. The steam cracking of such feeds favors the production ofbutadiene, but also produces heavier olefins and aromatics. Thus, thebutadiene resulting from the cracking step is typically extracted into apolar solvent from which it is then stripped by distillation. Butadieneis subjected to a hydrocyanation process in the presence of a nickelcatalyst to produce adiponitrile. See, for example, U.S. Pat. No.6,331,651. HMDA is then produced typically by the hydrogenation ofadiponitrile in the presence of a solid catalyst. See, for example, U.S.Pat. No. 4,064,172 (which discloses a process for producing HMDA byhydrogenating adiponitrile in the presence of an iron oxide catalyst)and U.S. Pat. No. 5,151,543 (which discloses that HMDA can be preparedby hydrogenating adiponitrile in the presence of a Raney nickel typecatalyst doped with at least one metal element selected from Groups 4,5, and 6 of the periodic table of the elements and, more recently,WO-A-93/16034 and WO-A-96/18603 (each of which discloses Raney nickelcatalyst based processes for the production of HMDA from adiponitrile)and US Patent Application No. 2003/0144552 (which discloses a processfor producing HMDA from adiponitrile in the presence of a particularlyconditioned Raney nickel catalyst).

Notably, each of the above-mentioned documents directed to theproduction of HMDA acknowledges the need for improvement in theefficiency, selectivity and commercial competitiveness of such process.In fact, the need for improved or alternative commercial processes forthe production of HMDA is exacerbated by the evolution of the chemicalindustry toward the use of lighter feeds which, when subjected tocracking, produce lesser amounts of butadiene and ultimately will leadto increased costs of producing HMDA and increased price volatility.

For many years there has been an interest in using biorenewablematerials as a feedstock to replace or supplement crude oil. See, forexample, Klass, Biomass for Renewable Energy, Fuels, and Chemicals,Academic Press, 1998, which is incorporated herein by reference.

Recently, HMDA and other chemicals used in the production of, amongothers materials, polymers such as nylon have been identified aschemicals that may be producible from biorenewable resources,particularly carbohydrate containing materials from which glucose can beobtained and used as the feedstock to manufacture such chemicals. See,for example, US 2010/0317069, which discloses biological pathwayspurported to be useful to produce, among other chemicals, caprolactamand HMDA.

To date, there is no commercially viable process for the production ofHMDA from carbohydrate containing feedstocks. Given the shift away fromthe production of conventional, oil-derived starting materials such asbutadiene, notwithstanding the continuing growth in the markets fornylons and polyurethanes, among other materials, derived at least inpart from HMDA or derivatives thereof and the benefits attributable tothe use of renewable feedstocks in lieu of petroleum derived feedstocks,new, industrially scalable methods for the selective andcommercially-meaningful production of chemicals frompolyhydroxyl-containing biorenewable materials (e.g., glucose derivedfrom starch, cellulose or sucrose) to important chemical intermediatessuch as HMDA is compelling.

1,6-hexanediol (HDO) has been prepared from, for example, adipic acid,caprolactone and hydroxycaproic acid. See, for example, U.S. Pat. No.5,969,194. Recently, a process for the production of 1,6-hexanediol fromfurfural derived from glucose has been disclosed in WO2011/149339. The'339 application provides a general description of at least a two stepcatalytic process for the production of HDO from 5-hydroxymethylfurfural(HMF): hydrogenation of HMF to 2,5-bis(hydroxymethyl)tetrahydrofuran(BHMTHF, also referred to as 2,5-tetrahydrofuran-dimethanol or THFDM)followed by hydrogenation of BHMTHF to 1,2,6-hexanetriol (HTO); and thenhydrogenation of 1,2,6-hexanetriol to 1,6-hexanediol. The processesdisclosed in the '339 application require at least two differentcatalyst systems to produce 1,6-hexanediol from HMF. Furthermore, thereported yields of HDO from HMF ranging from 4% (directly to HDO) to 22%(using a 3 step process: HMF to THFDM, THFDM to HTO, and then HTO toHDO). The low yields reported in the '339 application clearlydemonstrate the need for development of alternative, more efficientprocesses for the production of HDO.

SUMMARY

Briefly, therefore, the present invention is directed to processes forpreparing hexamethylenediamine from a carbohydrate source by convertinga carbohydrate source to a furfural substrate; reacting at least aportion of the furfural substrate with hydrogen in the presence of aheterogeneous reduction catalyst to produce 1,6-hexanediol; and,converting at least a portion of the 1,6-hexanediol tohexamethylenediamine. The present invention is also directed toprocesses for preparing hexamethylenediamine from a carbohydrate sourceby converting a carbohydrate source to a furfural substrate; reacting atleast a portion of the furfural substrate with hydrogen in the presenceof a heterogeneous reduction catalyst comprising Pt to produce areaction product comprising 1,2,6-hexanetriol; converting at least aportion of the 1,2,6-hexanetriol to 1,6-hexanediol; and converting atleast a portion of the 1,6-hexanediol to hexamethylenediamine. In someembodiments, the heterogeneous reduction catalyst comprises Pt. In otherembodiments, the heterogeneous reduction catalyst further comprises atleast one metal selected from the group consisting of Mo, La, Sm, Y, W,and Re. In other embodiments, the step of converting at least a portionof the 1,2,6-hexanetriol to 1,6-hexanediol is conducted in the presenceof hydrogen and a hydrogenation catalyst comprising Pt. In otherembodiments, the yield of 1,6-hexanediol is at least about 40%. In otherembodiments, the yield of 1,6-hexanediol is at least about 50%. In otherembodiments, the yield of 1,6-hexanediol is at least about 60%. In otherembodiments, the reaction of the furfural substrate with hydrogen iscarried out at a temperature in the range of about 60° C. and about 200°C. and a pressure of hydrogen in the range of about 200 psig to about2000 psig. In other embodiments, the furfural substrate is5-hydroxymethylfurfural. In other embodiments, the carbohydrate sourceis glucose, fructose, or a mixture comprising glucose and fructose. Inother embodiments, the catalyst further comprises a support selectedfrom the group consisting of zirconias, silicas and zeolites. In otherembodiments, the reaction of the furfural substrate with hydrogen iscarried out at a temperature in the range of about 100° C. and about180° C. and a pressure of hydrogen in the range of about 200 psig toabout 2000 psig. In other embodiments, the hydrogenation catalystcomprises Pt and W supported on zirconia. The present invention is alsodirected to hexamethylenediamine produced by the processes of any of theabove embodiments.

The present invention is also directed to processes for preparing1,6-hexanediol from a carbohydrate source by converting the carbohydratesource to a furfural substrate; and, reacting at least a portion of thefurfural substrate with hydrogen in the presence of a heterogeneousreduction catalyst comprising Pt to produce 1,6-hexanediol. The presentinvention is also directed to processes for preparing 1,6-hexanediolfrom a carbohydrate source by converting the carbohydrate source to afurfural substrate; reacting at least a portion of the furfuralsubstrate with hydrogen in the presence of a Pt containing heterogeneousreduction catalyst to produce a reaction product comprising1,2,6-hexanetriol; and, converting at least a portion of the1,2,6-hexanetriol to 1,6-hexanediol. In some embodiments, theheterogeneous catalyst further comprises at least one metal selectedfrom the group consisting of Mo, La, Sm, Y, W, and Re. In otherembodiments, the step of converting at least a portion of the1,2,6-hexanetriol to 1,6-hexanediol is conducted in the presence ofhydrogen and a hydrogenation catalyst comprising Pt. In otherembodiments, the hydrogenation catalyst is a supported heterogeneouscatalyst. In other embodiments, the yield of 1,6-hexanediol from thefurfural substrate is at least 40%. In other embodiments, the yield of1,6-hexanediol from the furfural substrate is at least 50%. In otherembodiments, the yield of 1,6-hexanediol from the furfural substrate isat least 60%. In other embodiments, the reaction of the furfuralsubstrate with hydrogen is carried out at a temperature in the range ofabout 60° C. and about 200° C. and a pressure of hydrogen in the rangeof about 200 psig to about 2000 psig. In other embodiments, the furfuralsubstrate is 5-hydroxymethylfurfural. In other embodiments, thecarbohydrate source is glucose, fructose, or a mixture comprisingglucose and fructose. In other embodiments, the catalyst furthercomprises a support selected from the group consisting of zirconias,silicas and zeolites. In other embodiments, the reaction of the furfuralsubstrate with hydrogen to produce 1,2,6-hexanetriol is carried out at atemperature in the range of about 100° C. and about 140° C. and apressure of hydrogen in the range of about 200 psig to about 1000 psig.In other embodiments, the catalyst comprises Pt and W supported onzirconia. The present invention is also directed to 1,6-hexanediolproduced by the processes of any of the above embodiments.

The present invention is also directed to processes for preparinghexamethylenediamine from a carbohydrate source by: (a) converting acarbohydrate source to a furfural substrate; (b) reacting at least aportion of the furfural substrate with hydrogen in the presence of aheterogeneous reduction catalyst comprising Pt to a reaction productcomprising 1,2,6-hexanetriol; (c) reacting at least a portion of the1,2,6-hexanetriol with hydrogen in the presence of the heterogeneousreduction catalyst comprising Pt to produce 1,6-hexanediol; and (d)converting at least a portion of the 1,6-hexanediol tohexamethylenediamine, wherein steps b) and c) are conducted in a singlereactor. The present invention is also directed to processes forpreparing 1,6-hexanediol from a carbohydrate source by: (a) converting acarbohydrate source to a furfural substrate; (b) reacting at least aportion of the furfural substrate with hydrogen in the presence of aheterogeneous reduction catalyst comprising Pt to a reaction productcomprising 1,2,6-hexanetriol; and (c) reacting at least a portion of the1,2,6-hexanetriol with hydrogen in the presence of the heterogeneousreduction catalyst comprising Pt to produce 1,6-hexanediol, whereinsteps b) and c) are conducted in a single reactor. In some embodiments,the heterogeneous reduction catalyst further comprises W. In otherembodiments, steps (b) and (c) are carried out at a temperature in therange of about 60° C. and about 200° C. and a pressure of hydrogen inthe range of about 200 psig to about 2000 psig. In other embodiments,the Pt containing catalysts of steps b) and c) are different and thetemperatures and pressures at which steps b) and c) are conducted aresubstantially the same. In other embodiments, the temperatures andpressures at which steps b) and c) are conducted are different. In otherembodiments, step b) is conducted at a temperature in the range of about100° C. to about 140° C. and a pressure in the range of about 200 psigto about 1000 psig and step c) is conducted at a temperature in therange of about 120° C. to about 180° C. and a pressure in the range ofabout 200 psig to about 2000 psig. In other embodiments, the yield of1,6-hexanediol from the furfural substrate is at least about 40%. Inother embodiments, the yield of 1,6-hexanediol from the furfuralsubstrate is at least about 50%. In other embodiments, the yield of1,6-hexanediol from the furfural substrate is at least about 60%. Inother embodiments, the carbohydrate source is glucose, fructose, or amixture comprising glucose and fructose. In other embodiments, steps (b)and (c) are carried out in one reaction zone. In other embodiments, thecatalyst comprises Pt and W supported on zirconia. The present inventionis also directed to hexamethylenediamine produced by the processes ofany of the above embodiments. The present invention is also directed to1,6-hexanediol prepared by the process of any of the above embodiments.

The present invention is also directed to processes for preparing acompound of formula II

wherein each of X² and X³ is selected from the group of hydrogen andhydroxyl; by converting a carbohydrate source to a furfural substrate;and, reacting at least a portion of the furfural substrate with hydrogenin the presence of a heterogeneous reduction catalyst comprising Pt toproduce the compound of formula II. In some embodiments, the catalystfurther comprises W. In other embodiments, the catalyst furthercomprises at least one metal selected from the group consisting of Mo,La, Sm, Y, W, and Re.

DETAILED DESCRIPTION

The following description sets forth exemplary methods, parameters andthe like. It should be recognized, however, that such description is notintended as a limitation on the scope of the present invention.

In accordance with the present invention, applicants disclose processesfor the chemocatalytic conversion of a furfural substrate, which may bederived from a carbohydrate source (e.g., glucose or fructose) tohexamethylenediamine, and intermediate processes and products along thepathway. In some embodiments, the processes are carried out byconverting a carbohydrate source to a furfural substrate; reacting atleast a portion of the furfural substrate with hydrogen in the presenceof a heterogeneous reduction catalyst to produce 1,6-hexanediol; and,converting at least a portion of the 1,6-hexanediol tohexamethylenediamine. In other embodiments, the processes are carriedout by converting a carbohydrate source to a furfural substrate;reacting at least a portion of the furfural substrate with hydrogen inthe presence of a heterogeneous reduction catalyst comprising Pt toproduce a reaction product comprising 1,2,6-hexanetriol; converting atleast a portion of the 1,2,6-hexanetriol to 1,6-hexanediol; andconverting at least a portion of the 1,6-hexanediol tohexamethylenediamine. In some embodiments, the processes are carried outby converting the carbohydrate source to a furfural substrate; and,reacting at least a portion of the furfural substrate with hydrogen inthe presence of a heterogeneous reduction catalyst comprising Pt toproduce 1,6-hexanediol. In other embodiments, the processes are carriedout by converting the carbohydrate source to a furfural substrate;reacting at least a portion of the furfural substrate with hydrogen inthe presence of a Pt containing heterogeneous reduction catalyst toproduce a reaction product comprising 1,2,6-hexanetriol; and, convertingat least a portion of the 1,2,6-hexanetriol to 1,6-hexanediol. In otherembodiments, the processes are carried out by (a) converting acarbohydrate source to a furfural substrate; (b) reacting at least aportion of the furfural substrate with hydrogen in the presence of aheterogeneous reduction catalyst comprising Pt to a reaction productcomprising 1,2,6-hexanetriol; (c) reacting at least a portion of the1,2,6-hexanetriol with hydrogen in the presence of the heterogeneousreduction catalyst comprising Pt to produce 1,6-hexanediol; and (d)converting at least a portion of the 1,6-hexanediol tohexamethylenediamine, wherein steps b) and c) are conducted in a singlereactor. In other embodiments, the processes are carried out by (a)converting a carbohydrate source to a furfural substrate; (b) reactingat least a portion of the furfural substrate with hydrogen in thepresence of a heterogeneous reduction catalyst comprising Pt to areaction product comprising 1,2,6-hexanetriol; and (c) reacting at leasta portion of the 1,2,6-hexanetriol with hydrogen in the presence of theheterogeneous reduction catalyst comprising Pt to produce1,6-hexanediol, wherein steps b) and c) are conducted in a singlereactor. In preferred embodiments, the 1,6-hexanediol is converted tohexamethylenediamine by a chemocatalytic amination reaction.

In another aspect of the invention, the hexamethylenediamine prepared inaccordance with the disclosed processes may be converted, according toprocesses known in the art, to various other industrially significantchemicals and chemical precursors including, for example, nylon 6,6 andmonomers for polyurethanes.

Biorenewable sources such as corn grain (maize), sugar beet, sugar caneas well as energy crops, plant biomass, agricultural wastes, forestryresidues, sugar processing residues, plant-derived household wastes,municipal waste, spent paper, switch grass, miscanthus, cassaya, trees(hardwood and softwood), vegetation, crop residues (e.g., bagasse andcorn stover) are all rich in hexoses, which can be used to producefurfural derivatives, such as 5-(hydroxmethyl)furfural. Hexoses can bereadily produced from such carbohydrate sources by hydrolysis. It isalso generally known that biomass carbohydrates can be enzymaticallyconverted to glucose, fructose and other sugars. Dehydration of fructosecan readily produce furan derivatives such as 5-(hydroxmethyl)furfural.Acid hydrolysis of glucose is also known to produce5-(hydroxmethyl)furfural; see, for example, U.S. Pat. No. 6,518,440.Various other methods have been developed for producing5-(hydroxmethyl)furfural including, for example, those described in U.S.Pat. No. 4,533,743 (to Medeiros et al.); U.S. Pat. No. 4,912,237 (toZeitsch); U.S. Pat. No. 4,971,657 (to Avignon et al.); U.S. Pat. No.6,743,928 (to Zeitsch); U.S. Pat. No. 2,750,394 (to Peniston); U.S. Pat.No. 2,917,520 (to Cope); U.S. Pat. No. 2,929,823 (to Garber); U.S. Pat.No. 3,118,912 (to Smith); U.S. Pat. No. 4,339,387 (to Fleche et al.);U.S. Pat. No. 4,590,283 (to Gaset et al.); and U.S. Pat. No. 4,740,605(to Rapp). In the foreign patent literature, see GB 591,858; GB 600,871;and GB 876,463, all of which were published in English. See also, FR2,663,933; FR 2,664,273; FR 2,669,635; and CA 2,097,812, all of whichwere published in French. Thus, a variety of carbohydrate sources can beused to produce 5-(hydroxymethyl)furfural by a variety of knowntechniques.

In some preferred embodiments, the carbohydrate source is glucose, andthe glucose is converted to fructose using methods known in the art,such as the industrial process to convert glucose into high-fructosecorn syrup. As above described, a variety of processes have beendisclosed directed to the production of a furfural substrate (e.g.,5-(hydroxymethyl)furfural) from, for example, glucose or other hexoses.

I. Furfural Substrate and Reduction Thereof

Applicants have discovered that a compound of formula II, below, can beprepared by chemocatalytically reacting a furfural substrate of formulaI with hydrogen in the presence of an heterogeneous catalyst comprisingplatinum (Pt) in accordance with the following overall reaction:

wherein each X² and X³ is independently hydrogen or hydroxyl. Inaccordance with various embodiments of the present invention, X² may behydrogen or hydroxyl and X³ is, preferably, hydrogen.

In various embodiments, the reaction is conducted in the presence of Ptcontaining catalysts at temperature(s) in the range of about 60° C. toabout 200° C. and pressure(s) in the range of about 200 psig to about2000 psig.

In accordance with various embodiments of the present invention, acompound of formula IIa can be prepared by chemocatalytically converting5-(hydroxmethyl)furfural (HMF) to a reaction product comprising thecompound of formula IIa by reacting HMF with hydrogen in the presence ofcatalyst comprising Pt in accordance with the following overallreaction:

wherein X² is hydroxyl or hydrogen.

In accordance with further embodiments of the present invention,5-(hydroxmethyl)furfural is initially reacted with hydrogen in thepresence of a catalyst comprising Pt under a first set of reactionconditions to convert at least a portion of the 5-(hydroxmethyl)furfuralto 1,2,6-hexanetriol, and at least a portion of the 1,2,6-hexanetriol issubsequently converted to 1,6-hexanediol in the presence of a catalystcomprising Pt under a second set of reaction conditions in accordancewith the following overall reaction:

In certain embodiments of the invention, the first reduction reaction toconvert 5-(hydroxmethyl)furfural to a reaction product comprising1,2,6-hexantriol and the second reduction reaction to convert at least aportion of the 1,2,6-hexantriol to 1,6-hexanediol may be accomplished ina single reaction zone wherein the reaction conditions are modifiedafter a defined period of time to effect the conversion of the triol tothe diol.

In various other embodiments of the present invention, the firstreduction reaction and the second reduction reaction are undertaken infinite zones of a single reactor, e.g., a fixed bed trickle flowreactor, wherein in a first zone is housed a first reduction catalystoperating under reaction conditions to produce a reaction productcomprising 1,2,6 hexanetriol and in a second reaction zone is housed asecond reduction catalyst operating under reaction conditions to convertat least a portion of the triol to 1,6 hexanediol. In such embodiments,the catalysts may be the same or different and the first set of reactionconditions and the second set of reaction conditions may be the same ordifferent. In some embodiments, the first set of reaction conditionscomprises a temperature in the range of about 60° C. to about 200° C.and a pressure in the range of about 200 psig to about 2000 psig. Insome embodiments, the second set of reaction conditions comprises atemperature in the range of about 80° C. to about 200° C. and a pressurein the range of about 500 psig to about 2000 psig.

Catalysts suitable for the hydrogenation reactions (reduction catalysts)are particular supported heterogeneous catalysts comprising Pt. In allembodiments of the present invention the catalysts comprise platinum asPt(0), alone or in combinations with other metals and/or alloys, whichis present on at least an external surface of a support (i.e., a surfaceexposed to the reaction constituents). In accordance with certainembodiments of the present invention, the catalysts employed in theprocesses comprise Pt and at least one metal selected from the group ofMo, La, Sm, Y, W, and Re (M2). In various embodiments of the inventionone or more other d-block metals, one or more rare earth metals (e.g.lanthanides), and/or one or more main group metals (e.g. Al) may also bepresent in combination with the Pt and M2 combinations. Typically, thetotal weight of metal(s) is from about 0.1% to about 10%, or from 0.2%to 10%, or from about 0.2% to about 8%, or from about 0.2% to about 5%,of the total weight of the catalyst. In more preferred embodiments thetotal weight of metal of the catalyst is less than about 4%.

The molar ratio of Pt (M1) to (M2) may vary, for example, from about20:1 to about 1:10. In various preferred embodiments, the M1:M2 molarratio is in the range of from about 10:1 to about 1:5. In still morepreferred embodiments, the ratio of M1:M2 is in the range of about 8:1to about 1:2.

In accordance with the present invention, the preferred catalyst is asupported, heterogeneous catalyst wherein the catalysts are on thesurface of the support. Suitable supports include, for example, acidicion-exchange resin, gamma alumina, fluorinated alumina, sulfate ortungstate promoted zirconia, titania, silica, silica promoted alumina,aluminum phosphate, tungsten oxide supported on silica-alumina, acidicclay, supported mineral acid, and zeolites. The support materials may bemodified using methods known in the art such as heat treatment, acidtreatment or by the introduction of a dopant (for example, metal-dopedtitanias, metal-doped zirconias (e.g., tungstated-zirconia), metal-dopedcerias, and metal-modified niobias). Preferred supports includezirconias, silicas, and zeolites. When a catalyst support is used, themetals may be deposited using procedures known in the art including, butnot limited to incipient wetness, ion-exchange,deposition-precipitation, and vacuum impregnation. When two or moremetals are deposited on the same support, they may be depositedsequentially or simultaneously. In various embodiments, following metaldeposition, the catalyst is dried at a temperature in the range of about20° C. to about 120° C. for a period of time ranging from at least about1 hour to about 24 hours. In these and other embodiments, the catalystis dried under sub-atmospheric pressure conditions. In variousembodiments, the catalyst is reduced after drying (e.g., by flowing 5%H₂ in N₂ at a temperature of at least about 200° C. for a period of timee.g., at least about 3 hours). Still further, in these and otherembodiments, the catalyst is calcined in air at a temperature of atleast about 200° C. for a period of time of at least about 3 hours.

The hydrogenation reaction(s) can also be conducted in the presence of asolvent to the furfural substrate. Solvents suitable for use inconjunction with the hydrogenation reaction to convert furfural toreaction product comprising diol or triol may include, for example,water, alcohols, esters, ethers, ketones, or mixtures thereof. Invarious embodiments, the preferred solvent is water.

In general, the hydrogenation reactions can be conducted in a batch,semi-batch, or continuous reactor design using fixed bed reactors,trickle bed reactors, slurry phase reactors, moving bed reactors, or anyother design that allows for heterogeneous catalytic reactions. Examplesof reactors can be seen in Chemical Process Equipment—Selection andDesign, Couper et al., Elsevier 1990, which is incorporated herein byreference. It should be understood that the furfural substrate (e.g.,5-(hydroxymethyl)furfural), hydrogen, any solvent, and the catalyst maybe introduced into a suitable reactor separately or in variouscombinations.

The chemocatalytic conversion of a furfural substrate to 1,6-hexanediol,either as two separate chemocatalytic reduction steps or as a combinedchemocatalytic reduction step, may yield a mixture of products. Forexample, when the furfural substrate is 5-(hydroxmethyl)furfural, thereaction product mixture may include not only 1,6-hexanediol and/or1,2,6-hexanetriol, but also lesser amounts of 1,5-hexanediol; 1,2,5hexanetriol; 1,2,5,6-hexanequatrol; 1-hexanol; and 2-hexanol. Theproduction of 1,6-hexanediol from the furfural substrate (e.g.,5-(hydroxmethyl)furfural) is unexpectedly quite facile. In severalembodiments, at least 50%, at least 60%, or at least 70% of the productmixture is 1,2,6-hexanetriol. In several embodiments, the production ofHDO is at least about 40%, at least about 50% or at least about 60%.

The product mixture may be separated into one or more products by anysuitable methods known in the art. In some embodiments, the productmixture can be separated by fractional distillation under subatmosphericpressures. For example, in some embodiments, 1,6-hexanediol can beseparated from the product mixture at a temperature between about 90° C.and about 110° C.; 1,2,6-hexanetriol can be separated from the productmixture at a temperature between about 150° C. and 175° C.;1,2-hexanediol and hexanol can be separated from the product mixture ata temperature between about 100° C. and 125° C. In certain embodiments,1,2,6-hexanetriol can be isolated from the product mixture, and recycledin a further reduction reaction to produce additional 1,6-hexanediol.The 1,6-hexanediol may be recovered from any remaining other products ofthe reaction mixture by one or more conventional methods known in theart including, for example, solvent extraction, crystallization orevaporative processes.

In accordance with the present invention the production of HDO from thesubstrate of formula I can be conducted at reaction temperatures in therange of from about 60° C. to about 200° C., more typically in the rangeof from about 80° C. to about 200° C. In various preferred embodiments,the step of converting the furfural to 1,2,6-hexanetriol is conducted atreaction temperatures in the range of from about 100° C. to about 140°C. and the conversion of 1,2,6-hexanetriol to 1,6-hexanediol isconducted at reaction temperatures in the range of from about 120° C. toabout 180° C. In accordance with the present invention the production ofHDO from the substrate of formula I can be conducted at hydrogenpressures in the range of from about 200 psig to about 2000 psig. Invarious preferred embodiments, the step of converting the furfural to1,2,6-hexanetriol is conducted at hydrogen pressure in the range of fromabout 200 psig to about 1000 psig and the conversion of1,2,6-hexanetriol to 1,6-hexanediol is conducted at hydrogen pressure inthe range of from about 200 psig to about 2000 psig.

II. Preparation of Hexamethylenediamine from 1,6-Hexanediol

The preparation of hexamethylenediamine from 1,6-hexanediol may becarried out using procedures known in the art. See, for example, theprocesses disclosed in U.S. Pat. Nos. 2,754,330; 3,215,742; 3,268,588;and 3,270,059.

When introducing elements of the present invention or the preferredembodiments(s) thereof, the articles “a”, “an” are intended to be thesingular unless the context admits otherwise and “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are not intended to be inclusiveand use of such terms mean that there may be additional elements otherthan the listed elements.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above compositions and processeswithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

Having described the invention in detail, it will be apparent thatmodifications and variations are possible without departing from thescope of the invention defined in the appended claims.

EXAMPLES

The following non-limiting examples are provided to further illustratethe present invention.

Reactions were conducted in 1 mL glass vials housed in a pressurizedvessel in accordance with the procedures described in the examplesbelow. Conversion, product yields and selectivity were determined usingion chromatography with electro-chemical detection.

Example 1: Conversion of Hydroxymethylfurfural to 1,6-Hexanediol

Samples of Silica Cariact Q-10 (Fuji Silysia) support were dried at 60°C. Suitably concentrated aqueous solutions of (NH₄)₆Mo₇O₂₄ were added to˜10 mg of solids and agitated to impregnate the supports. The solidswere calcined at 600° C. in air for 3 hours. Subsequently, suitablyconcentrated aqueous solutions of Pt(NO₃)₂ were added to ˜10 mg ofsolids and agitated to impregnate the supports. The samples were driedin an oven at 60° C. overnight under a dry air purge. Then reduced at350° C. under forming gas (5% H₂ and 95% N₂) atmosphere for 3 hours with5° C./min temperature ramp rate. The final catalysts were composed ofca. 3.9 wt % Pt & 1.3 wt % Mo.

These catalysts were tested for hydroxymethylfurfural reduction usingthe following catalyst testing protocol. Catalyst (ca. 8 mg) was weighedinto a glass vial insert followed by addition of an aqueoushydroxymethylfurfural solution (200 μl of 0.1 M). The glass vial insertwas loaded into a reactor and the reactor was closed. The atmosphere inthe reactor was replaced with hydrogen and pressurized to 670 psig atroom temperature. Reactor was heated to 160° C. and maintained at therespective temperature for 300 minutes while vials were shaken. After300 minutes, shaking was stopped and reactor was cooled to 40° C.Pressure in the reactor was then slowly released. The glass vial insertwas removed from the reactor and centrifuged. The clear solution wasdiluted with methanol and analyzed by gas chromatography with flameionization detection. The results are reported in Table 1:

TABLE 1 HMF BHMTH 1.6-Hexanediol 1.2,6-Hexanetriol Conversion 1.2,6-HT FYield (%), Yield (%), Entry Metals Support (%) Yield (%) Yield (%)(Selectivity %) (Selectivity %) 1 Pt—Mo Silica 87 12 1 14 (16) 48 (50)Cariact

Example 2: Conversion of Hydroxymethylfurfural to 1,2,6-Hexanetriol

Samples of Alumina support were dried at 120° C. Suitably concentratedaqueous solutions of Pt(NO₃)₂ were added to ˜8 mg of solids and agitatedto impregnate the supports. The solids were dried at 120° C. in air for16 hours. Subsequently, suitably concentrated aqueous solutions of(NH₄)₆Mo₇O₂₄ or La(NO₃)₃ or Sm(NO₃)₂ were added to ˜8 mg of solids andagitated to impregnate the supports. The samples were dried in an ovenat 120° C. overnight under air. Then calcined at 500° C. under air for 3hours with 30° C./min temperature ramp rate. The final catalysts werecomposed of ca. 4 wt % Pt and various M2 loadings (see Table 2).

These catalysts were tested for hydroxymethylfurfural reduction usingthe following catalyst testing protocol. Catalyst (ca. 8 mg) was weighedinto a glass vial insert followed by addition of an aqueoushydroxymethylfurfural solution (250 μl of 0.4 M). The glass vial insertwas loaded into a reactor and the reactor was closed. The atmosphere inthe reactor was replaced with hydrogen and pressurized to 200 psig atroom temperature. Reactor was heated to 120° C. and maintained at therespective temperature for 300 minutes while vials were shaken. After300 minutes, shaking was stopped and reactor was cooled to 40° C.Pressure in the reactor was then slowly released. The glass vial insertwas removed from the reactor and centrifuged. The clear solution wasdiluted with methanol and analyzed by gas chromatography with flameionization detection. The results are reported in Table 2.

TABLE 2 M2:Pt Support HMF 1.2,6-HT Yield (%), Entry Metals mol:molSupport Supplier Conversion (%) (Selectivity %) 1 Pt—Mo 0.5 CataloxAlumina SBa-200 Sasol 100 48 (50) 2 Pt—Mo 0.25 Alumina AL 2100 DavicatGrace Davison 100 50 (51) 3 Pt—La 1 Catalox Alumina SBa-90 Sasol 100 51(50) 4 Pt—Sm 1 Catalox Alumina SBa-90 Sasol 100 51 (50)

Example 3: Conversion of 1,2,6-Hexanetriol to 1,6-Hexanediol

Samples of Zirconia SZ 61143 (Saint-Gobain Norpro) support were calcinedat 750-800° C. in air for 0.5-2 hours. Suitably concentrated aqueoussolutions of Pt(NO₃)₂ were added to ˜10 mg of solids and agitated toimpregnate the supports. The samples were dried in an oven at 60° C.overnight under a dry air purge. Then reduced at 350° C. under forminggas (5% H₂ and 95% N₂) atmosphere for 3 hours with 5° C./min temperatureramp rate. The final catalysts were composed of ca. 3.9 wt % Pt.

These catalysts were tested for 1,2,6-hexanetriol reduction using thefollowing catalyst testing protocol. Catalyst (ca. 10 mg) was weighedinto a glass vial insert followed by addition of an aqueous1,2,6-hexanetriol solution (200 μl of 0.2 M). The glass vial insert wasloaded into a reactor and the reactor was closed. The atmosphere in thereactor was replaced with hydrogen and pressurized to 670 psig at roomtemperature. Reactor was heated to 160° C. and maintained at therespective temperature for 150 minutes while vials were shaken. After150 minutes, shaking was stopped and reactor was cooled to 40° C.Pressure in the reactor was then slowly released. The glass vial insertwas removed from the reactor and centrifuged. The clear solution wasdiluted with methanol and analyzed by gas chromatography with flameionization detection. The results are reported in Table 3.

TABLE 3 1,2,6-Hexanetriol 1.6-Hexanediol Yield (%), Entry Metals SupportSupport Treatment Conversion (%) (Selectivity %) 1 Pt Zirconia SZ 61143750° C./2 hr 91 61 (68) 2 Pt Zirconia SZ 61143 800° C./0.5 hr 95 59 (63)3 Pt Zirconia SZ 61143 750° C./1 hr 95 58 (62)

Example 4: Conversion of 1,2,6-Hexanetriol to 1,6-Hexanediol

Samples of Silica Cariact Q-10 (Fuji Silysia) support were dried at 60°C. Suitably concentrated aqueous solutions of (NH₄)₆Mo₇O₂₄ or(NH₄)₁₀W₁₂O₄₁ were added to ˜10 mg of solids and agitated to impregnatethe supports. The solids were calcined at 600° C. in air for 3 hours.Subsequently, suitably concentrated aqueous solutions of Pt(NO₃)₂ wereadded to ˜10 mg of solids and agitated to impregnate the supports. Thesamples were dried in an oven at 60° C. overnight under a dry air purge.Then reduced at 350° C. under forming gas (5% H₂ and 95% N₂) atmospherefor 3 hours with 5° C./min temperature ramp rate. The final catalystswere composed of ca. 3.9 wt % Pt & 0.8 wt % Mo or 3.9 wt % Pt & 1.3 wt %W.

These catalysts were tested for 1,2,6-hexanetriol reduction using thefollowing catalyst testing protocol. Catalyst (ca. 10 mg) was weighedinto a glass vial insert followed by addition of an aqueous1,2,6-hexanetriol solution (200 μl of 0.2 M). The glass vial insert wasloaded into a reactor and the reactor was closed. The atmosphere in thereactor was replaced with hydrogen and pressurized to 670 psig at roomtemperature. Reactor was heated to 160° C. and maintained at therespective temperature for 150 minutes while vials were shaken. After150 minutes, shaking was stopped and reactor was cooled to 40° C.Pressure in the reactor was then slowly released. The glass vial insertwas removed from the reactor and centrifuged. The clear solution wasdiluted with methanol and analyzed by gas chromatography with flameionization detection. The results are reported in Table 4.

TABLE 4 1,2,6- 1.6-Hexanediol Hexanetriol Yield (%), Entry MetalsSupport Conversion (%) (Selectivity %) 1 Pt—Mo Silica Cariact Q-10 78 55(69) 2 Pt—W Silica Cariact Q-10 36 33 (92)

Example 5: Conversion of 1,2,6-Hexanetriol to 1,6,-Hexanediol

Suitably concentrated aqueous solutions of Pt(NO₃)₂ and (NH₄)₆Mo₇O₂₄were each added to about 10 mg of solids and agitated to impregnate thesupports. The sample was dried in an oven at 60° C. overnight under adry air purge. The dried sample was then reduced at 500° C. or 350° C.under forming gas (5% H₂ and 95% N₂) atmosphere for 3 hours with 5°C./min temperature ramp rate. The final catalyst was composed of about3.9 wt % Pt and 0.2 wt % Mo.

The catalyst was tested for 1,2,6-hexanetriol reduction using thefollowing catalyst testing protocol. Catalyst (ca. 10 mg) was weighedinto a glass vial insert followed by addition of an aqueous1,2,6-hexanetriol solution (200 μl of 0.2 M). The glass vial insert wasloaded into a reactor and the reactor was closed. The atmosphere in thereactor was replaced with hydrogen and pressurized to 830 or 670 psig atroom temperature. The reactor was heated to 160° C. The temperature wasmaintained for 5 hours while the vial was shaken. After 5 hours, shakingwas stopped and the reactor was cooled to 40° C. Pressure in the reactorwas then slowly released. The glass vial insert was removed from thereactor and centrifuged. The clear solution was diluted with deionizedwater, and analyzed by ion chromatography with electro-chemicaldetection. The results are summarized in Table 5 below.

TABLE 5 1,2,6-Hexanetriol Entry Metals Support Supplier Conversion (%)1.6-Hexanediol Yield (%), 1 Pt—Mo Silica Cariact G-10 Fuji Silysia 54 42

Example 6: Conversion of 1,2,6-Hexanetriol to 1,6-Hexanediol

Samples of Zeolite (Zeolyst) supports were dried at 60° C. Suitablyconcentrated aqueous solutions of (NH₄)₁₀W₁₂O₄₁ were added to ˜10 mg ofsolids and agitated to impregnate the supports. The solids were calcinedat 500° C. in air for 3 hours. Subsequently, suitably concentratedaqueous solutions of Pt(NO₃)₂ were added to ˜10 mg of solids andagitated to impregnate the supports. The samples were dried in an ovenat 60° C. overnight under a dry air purge. Then reduced at 350° C. underforming gas (5% H₂ and 95% N₂) atmosphere for 3 hours with 5° C./mintemperature ramp rate.

These catalysts were tested for 1,2,6-hexanetriol reduction using thefollowing catalyst testing protocol. Catalyst (ca. 10 mg) was weighedinto a glass vial insert followed by addition of an aqueous1,2,6-hexanetriol solution (200 μl of 0.2 M). The glass vial insert wasloaded into a reactor and the reactor was closed. The atmosphere in thereactor was replaced with hydrogen and pressurized to 670 psig at roomtemperature. Reactor was heated to 160° C. and maintained at therespective temperature for 150 minutes while vials were shaken. After150 minutes, shaking was stopped and reactor was cooled to 40° C.Pressure in the reactor was then slowly released. The glass vial insertwas removed from the reactor and centrifuged. The clear solution wasdiluted with methanol and analyzed by gas chromatography with flameionization detection. The results are summarized in Table 6 below.

TABLE 6 M2:Pt 1,2,6-Hexanetriol 1.6-Hexanediol Yield (%), Entry Metalsmol:mol Support Conversion (%) (Selectivity %) 1 Pt—W 0.33 Zeolite CBV720 (Y) 89 49 (60) 2 Pt—W 0.33 Zeolite CP811C-300 (Beta) 100 65 (65)

1-36. (canceled)
 37. A process for preparing 1,6-hexanediol comprisingreacting 1,2,6-hexanetriol with hydrogen in the presence of aheterogeneous reduction catalyst comprising a support selected from thegroup consisting of zirconias, silicas, and zeolites.